The present invention relates to sampling apparatus, and in particular to a sampling apparatus for extracting a sample of liquid product from a product flow line and for delivering the sample in a sanitary condition to a collection container.
Modern process control often requires that the immediate or overall composition of a liquid product flowing through a pipe or conduit be monitored. Such monitoring can be accomplished with apparatus that takes samples of the liquid from the main body thereof. Where a composite sample of the liquid flow is required, the sampler is usually operated to withdraw a series of small, precisely measured discrete amounts of the liquid as it passes the sampling point. The number of individual samples taken is adjusted according to time or by liquid product volume flow to generate a composite sample volume that represents the process material composition. Samples can be collected in a common container or in individual bottles as required.
Samplers are used to obtain samples of milk for analysis. Milk is received by a dairy from a number of individual dairy farmers and tank trucks transport the milk from the dairy farmers to the dairy. A single tank truck may receive milk from as many as ten different dairy farmers before delivering the load of milk to the dairy. Because the batches of milk supplied by the individual dairy farmers ordinarily differ in content, such as in percentage of butterfat, it is necessary to know the amount and content of the milk supplied by each dairy farmer in order to determine the payment due to the farmer.
A milk storage tank at each dairy farm has an agitator and a cooler to keep the milk thoroughly stirred and in a chilled condition, and at each dairy farm the operator of the tank truck "examines" the milk in the storage tank to determine whether to load it into the truck. The decision to load or not load the milk is based upon various tests such as smelling the milk, determining that it is properly agitated, and measuring the temperature of the milk to ensure that there will not be rapid spoilage.
If the truck operator determines that the milk in the storage tank seems to be satisfactory, it is loaded into the tank truck where it mixes with milk from other dairy farms. Prior to or during loading, the amount of milk supplied by the dairy farmer is determined and a sample of the milk is obtained for later analysis to determine its content. To obtain a sample the truck operator could hand dip a sample of milk from the dairy farm storage tank, but the procedure is expensive and time consuming and is prone to operator error. Instead, as the milk is flowed from the storage tank into the truck, the better practice is to periodically extract and collect discrete and measured amounts of milk from the flow to obtain a composite sample for analysis.
The operator of the tank truck obtains a sample of milk from each dairy farmer and each sample is analyzed at the dairy for such things as butterfat and calcium content, as well as for any undesirable substances such as bacteria, steroids, insecticides and other objectionable contaminants. The samples representing the various batches of milk in the truck may be analyzed before the truck is unloaded at the dairy. This enables a determination to be made as to whether a truck load of milk obtained from a group of dairy farmers is unacceptable before the milk in the truck is unloaded and mixed with other milk at the dairy.
In sampling milk, it is necessary to maintain the highest possible level of sanitation in order to avoid problems with bacterial build-up and contamination. Because sampling often occurs at the tank truck as a batch of milk from a dairy farmer's holding tank is flowed into the truck, the same sampler is used in sampling the different batches of milk flowed into the truck at the various dairy farms. The sampler should therefore be capable of being thoroughly cleaned and brought to a sanitary condition between uses to prevent cross-contamination of samples of milk as a result of bacteria or other contaminants being conveyed or carried over by the sampler from milk at one dairy farm to milk at the next.